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Q1) Write a rule for the nth term of the arithmetic sequence 1,6,11,16.... Then find a10.

A1) An=A1 + (n-1)d

An=1+ (n-1)5

A10=1+(10-1)5

A10=1+45

A10=46

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Q2) Find the sum of the first 20 terms of the arithmetic series:

.5+1.1+1.7+2.3+2.9+.....

A2) An=a1+(n-1)d

A20= .5 + (20-1).6

a20= 11.4+.5 = 11.9

Sn= n (a1+an/2)

sn= 10 (.5+11.9/12)

Sn=124

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Q3) Write a rule for the nth term of the geometric sequence 3,15,75,375,... then find a12

a3) An=A1r^(n-1)

an=(3)(5)^(n-1)

A12=(3)(5)^(12-1)

a12=(3)(5)^11

a12=146,484,375

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Q4) Your father wants to make a deal with you. He will giev you five cents to clean the garage. He will then double the amout daily for each day this month that you keep the garage tidy. Today is August 15. Is it a good idea to accept these conditions? How much will you earn on August 31?

A4) C= .5

n=number of days

Expression: an= 2c+n

an=2(.5)+n

an= n+1

A15=15+1

a15=16

He would earn $16 on august 31st.

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I do not know the answers for the following questions.

Q5) Write the next term in the sequence. Then write a rule for the nth term.

a) 7,-8,9,-10

Aa)

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b) (1/2), (-1/4), (1/8), (-1/16)..

Ab) i was thinking the rule could probably be 1/2^(n+2) but the problem is that i wont get the negative sign..

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Any help is much appreciated.

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# Homework Help: Arithmetic/Geometric sequences

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